It has been hypothesized that the initiation of bacterial pyelonephritis is due to the disruption of renal lysosomes by bacteria or their products. This hypothesis has been supported by: observations in experimental models of pyelonephritis in which it has been shown that only bacteria which are able to alter the integrity of renal lysosomes can produce pyelonephritis, ultrastructural studies which show early pathological changes of renal lysosomes and mitochondria only in animals receiving "lysosomal damaging" bacteria. Recent efforts have been directed at determining if the harmful effects of bacteria or their products on lysosomal integrity is a generalized mechanism whereby bacteria establish infection in organs other than the kidney as well. A correlation between hepatic lysosomal disruption and virulence with a variety of bacteria has been found in the liver. It is possible that the interaction between bacteria and lysosomes of specific organs may be the basis for the ability of certain bacteria to produce infections in particular organs.